The present invention relates to an EVA insole manufacturing process for making EVA (ethylene vinyl acetate copolymer resin) insoles.
U.S. Pat. No. 5,141,578 issued to the inventor of the present invention, discloses an EVA insole manufacturing process which includes a step of mixing an EVA resin with a foaming agent for producing a molding through an injection molding process, and a step of heating the molding thus obtained in a mold so that it foams into a predetermined shape. Two or more moldings which respectively contain a different concentration of foaming agent or a different pigment color may be put together in a common mold and subjected to integral foaming and form setting process, so as to produce an insole which has different hardness and color at different parts thereof. This EVA insole manufacturing process eliminates the disadvantages of a conventional EVA insole manufacturing process, which includes a first step to mix an EVA resin with a foaming agent and then squeezing the mixture into strips, a second step to place the EVA material strips in a hot press and letting it be subjected to a foaming process, a third step to place the foamed EVA strip in a water cooling trough for cooling and then cutting or trimming the foamed EVA strips, a fourth step to grind the EVA strips and then put them in a hydraulic machine for form setting. The EVA insole manufacturing process according to U.S. Pat. No. 5,141,578 consumes less human power, can fully utilize EVA material and greatly increase production capacity. However, it is still time consuming in forming a first molding and a second molding and form setting the integral molding obtained from putting the second molding within an opening on the first molding and heat foaming both the first and second moldings together in a mold. Further, this process needs much equipment including at least a crusher, an injection molding machine, a heat press, a hydraulic machine. Because of the use of the aforesaid necessary equipment, the hardware equipment cost and regular hardware equipment maintenance cost become inevitably high.